Patent application title: Steering wheel position adjustment device

Abstract:

A steering wheel position adjustment device includes a movable bracket
having adjusting long holes on both sides in a width direction of the
movable bracket, a fixed bracket, a lock shaft penetrating through both
of the adjusting long holes to support the movable bracket to the fixed
bracket, a collar member which is rotatably supported within the movable
bracket by the lock shaft and is capable of moving along, with the lock
shaft, in a longitudinal direction and stopper shock-absorbing materials,
which are attached to both side sections in the longitudinal direction of
the adjusting long holes within the movable bracket, and each of which is
formed thereon with an abutment surface against which the collar member
abuts.

Claims:

1. A steering wheel position adjustment device, comprising:a movable
bracket having adjusting long holes on both sides in a width direction of
the movable bracket;a fixed bracket;a lock shaft penetrating through both
of the adjusting long holes to support the movable bracket to the fixed
bracket;a collar member which is rotatably supported within the movable
bracket by the lock shaft and is capable of moving along, with the lock
shaft, in a longitudinal direction; andstopper shock-absorbing materials,
which are attached to both side sections in the longitudinal direction of
the adjusting long holes within the movable bracket, and each of which is
formed thereon with an abutment surface against which the collar member
abuts,wherein when each of the stopper shock-absorbing materials and the
collar member abut against each other, both end portions in a width
direction of the abutted surface of the stopper shock-absorbing material
are first brought into abutment.

2. The steering wheel position adjustment device according to claim 1,
wherein in the collar member, a cylindrical shape portion is formed in a
central portion in an axial direction of the collar member and conical
portions are formed such that a diameter of each of the conical portions
gradually increases toward both ends in a width direction of the
cylindrical shape portion, and wherein both of the end portions in the
width direction of the abutment surface of the stopper shock-absorbing
material abut against the conical portion.

3. The steering wheel position adjustment device according to claim 1,
wherein the central portion in the axial direction of the collar member
is a smallest diameter portion, and a cross-sectional shape of the collar
member along the axial direction is formed in a substantially arched
shape such that the diameter thereof gradually increases toward both
sides in the axial direction.

4. The steering wheel position adjustment device according to claim 1,
wherein the abutment surface has a substantially concave arched cross
section in the width direction thereof.

5. The steering wheel position adjustment device according to claim 1,
wherein edge projecting portions are formed on both of the end portions
in the width direction of the abutment surface of the stopper
shock-absorbing material.

6. The steering wheel position adjustment device according to claim 2,
wherein the abutment surface has a substantially concave arched cross
section in the width direction thereof.

7. The steering wheel position adjustment device according to claim 2,
wherein edge projecting portions are formed on both of the end portions
in the width direction of the abutment surface of the stopper
shock-absorbing material.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a steering wheel position
adjustment device in which a stopper shock-absorbing material for
absorbing shocks during tilt/telescopic adjustment can be mounted on a
predetermined position extremely easily and shock-absorbing capacity for
tilt/telescopic adjustment can be improved in a steering device having a
tilt/telescopic adjustment mechanism.

[0003]2. Description of the Related Art

[0004]A steering device with a tilt/telescopic adjustment mechanism, which
is capable of adjusting the position of the steering wheel vertically and
longitudinally in accordance with the physical constitution of a driver,
has been conventionally frequently used (see Unexamined Utility Model
Application Publication S64-28365 and Japanese Published Unexamined
Patent Application No. 2006-240327). In the structure of this steering
device having a tilt/telescopic adjustment mechanism, tilting and
telescopic long holes are formed in a bracket portion, and a lock lever
shaft and the like which penetrate through these long holes are inserted
and disposed. The problem in this structure is that when a metallic bolt
is moved along the long holes, end surfaces of the long holes, also made
of metal, collide with the bolt at a tilt/telescopic operation limit
position, thereby causing metallic clank and impairing quietness and soft
operational touch in the operation limit position when the bolt and the
end surfaces of the long holes hit against each other.

[0005]In order to prevent metallic contact between the bolt and the long
hole end portions of the bracket member, there is considered means for
absorbing shocks by attaching a stopper material formed by a rubber, a
synthetic resin or the like to the long hole end portions so that the
bolt shaft and the long hole end portions do not abut against each other
directly.

[0006]As disclosed in Unexamined Utility Model Application Publication
S64-28365 and Japanese Published Unexamined Patent Application No.
2006-240327, the stopper shock-absorbing material made of a rubber, a
synthetic resin or the like was attached, whereby it was possible to
absorb shocks and realize quietness. In recent years, however, as to
operational feeling in tilt/telescopic adjustment of the steering wheel,
it is required to provide automobiles with a higher level of quietness
and operational touch in tilt/telescopic adjustment. An object of the
present invention, therefore, is to improve operational feeling when
performing the adjustment, and particularly to reduce shocks and impact
noises that are caused at the time of operation.

SUMMARY OF THE INVENTION

[0007]Therefore, in order to solve the above-described problem, the
inventors have conducted keen research and, as a result, solved the
problem by configuring the invention of claim 1 as a steering wheel
position adjustment device, comprising: a movable bracket having
adjusting long holes on both sides in a width direction of the movable
bracket; a fixed bracket; a lock shaft penetrating through both of the
adjusting long holes to support the movable bracket to the fixed bracket;
a collar member which is rotatably supported within the movable bracket
by the lock shaft and is capable of moving along, with the lock shaft, in
a longitudinal direction; and stopper shock-absorbing materials, which
are attached to both side sections in the longitudinal direction of the
adjusting long holes within the movable bracket, and each of which is
formed thereon with an abutment surface against which the collar member
abuts, wherein when each of the stopper shock-absorbing materials and the
collar member abut against each other, both end portions in a width
direction of the abutted surface of the stopper shock-absorbing material
are first brought into abutment.

[0008]The above-described problem is solved by configuring the invention
of claim 2 as the steering wheel position adjustment device according to
the abovementioned configuration, wherein in the collar member, a
cylindrical shape portion is formed in a central portion in an axial
direction of the collar member and conical portions are formed such that
a diameter of each of the conical portions gradually increases toward
both ends in a width direction of the cylindrical shape portion, and
wherein both of the end portions in the width direction of the abutment
surface of the stopper shock-absorbing material abut against the conical
portion. The above-described problem is solved by configuring the
invention of claim 3 as the steering wheel position adjustment device
according to the abovementioned configuration, wherein the central
portion in the axial direction of the collar member is a smallest
diameter portion, and a cross-sectional shape of the collar member along
the axial direction is formed in a substantially arched shape such that
the diameter thereof gradually increases toward both sides in the axial
direction.

[0009]The above-described problem is solved by configuring the inventions
of claims 4 and 5 as the steering wheel position adjustment device
according to the abovementioned configuration, wherein the abutted
surface has a substantially concave arched cross section in the width
direction thereof. The above-described problem is solved by configuring
the inventions of claims 6 and 7 as the steering wheel position
adjustment device according to the abovementioned configuration, wherein
edge projecting portions are formed on the both end portions in the width
direction of the abutted surface of the stopper shock-absorbing material.

[0010]In the invention of claim 1, the abutted surface of the stopper
shock-absorbing material abuts against the collar member during
tilt/telescopic adjustment in a step in which the both end portions in
the width direction of the abutted surface are first brought into
abutment against collar member, and then the central section in the width
direction of the abutted surface abuts against or comes close to the
collar member. Accordingly, in the stopper shock-absorbing material, the
both end portions in the width direction of the abutted surface are
elastically deformed by abutting against the collar member, and shocks
are temporally dispersed as compared with the ordinary case where the
entire abutted surface abuts against the collar member at once, whereby
the shock force generated when the collar member and the stopper
shock-absorbing material hit against each other can be further reduced
and quietness and operational touch in telescopic adjustment can be
improved.

[0011]According to the invention of claim 2, the cylindrical shape portion
is formed in the central portion in the axial direction of the collar
member, the conical portions are formed on both sides in the width
direction of the cylindrical shape portion, respectively, such that the
diameters of the conical portions gradually increase toward respective
end portions in the axial direction of the collar member, and the width
direction of the abutted surface of the stopper shock-absorbing material
is formed to be larger than that of the cylindrical shape portion.
Accordingly, since the both end portions in the width direction of the
stopper shock-absorbing material are brought into abutment against the
conical portions of the collar member, the both end portions in the width
direction of the abutted surface in particular are elastically deformed
significantly, whereby shock absorption is extremely improved and
quietness and operational touch in telescopic adjustment can also be
improved.

[0012]According to the invention of claim 3, the central portion in the
axial direction of the collar member is configured as a smallest diameter
portion, and a cross-sectional shape along the axial direction of the
collar member is formed in a substantially arched shape such that the
diameter thereof gradually increases toward the both sides in the axial
direction. Accordingly, the both end portions and central portion in the
width direction of the stopper shock-absorbing material can be entirely
brought into abutment against the collar member smoothly, whereby
quietness can be achieved. According to the inventions of claims 4 and 5,
the abutment surface has a substantially concave arched cross section in
the width direction thereof. Therefore, it is sufficient that the collar
member be formed into a cylindrical shape only so that a simple structure
can be obtained. In the inventions of claims 6 and 7, edge projecting
portions are formed on both of the end portions in the width direction of
the abutted surface of the stopper shock-absorbing material. Therefore,
as with the effect of claims 4 and 7, it is sufficient that the collar
member be formed into a cylindrical shape only so that a simple structure
can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1A is a side view showing a partial cross section of a steering
device comprising the present invention;

[0014]FIG. 1B is a cross-sectional diagram taken along the arrow Xa-Xa of
FIG. 1A;

[0015]FIG. 1C is a cross-sectional diagram taken along the arrow Xb-Xb of
FIG. 1A;

[0016]FIG. 2A is an enlarged cross-sectional diagram showing a substantial
part of the present invention;

[0017]FIG. 2B is an enlarged cross-sectional diagram showing the shapes of
a collar member and of a stopper shock-absorbing material according to a
first embodiment;

[0018]FIG. 3 is an enlarged cross-sectional diagram showing a state in
which both end portions in a width direction of the stopper
shock-absorbing material of the first embodiment abut against conical
portions of the collar member of the first embodiment;

[0019]FIGS. 4A through 4C are operational diagrams each showing a step in
which the collar member of the first embodiment and the stopper
shock-absorbing material of the first embodiment abut against each other;

[0020]FIG. 5A is a cross-sectional diagram showing the configurations of a
collar member of a second embodiment and of the stopper shock-absorbing
material of the first embodiment;

[0021]FIGS. 5B and 5C are operational diagrams each showing a step in
which the collar member and the stopper shock-absorbing material abut
against each other;

[0022]FIG. 6A is a cross-sectional diagram showing the configurations of a
collar member of a third embodiment and of a first type of stopper
shock-absorbing material of the second embodiment;

[0023]FIGS. 6B and 6C are operational diagrams each showing a step in
which the collar member and the stopper shock-absorbing material abut
against each other;

[0024]FIG. 7A is a cross-sectional diagram showing the configurations of
the collar member of the third embodiment and of a second type of stopper
shock-absorbing material of the second embodiment;

[0025]FIGS. 7B and 7C are operational diagrams each showing a step in
which the collar member and the stopper shock-absorbing material abut
against each other;

[0026]FIG. 8A is a perspective view showing the stopper shock-absorbing
material of the first embodiment which corresponds to the collar members
of the first and second embodiments;

[0027]FIG. 8B is a cross-sectional diagram taken along the arrow Xc-Xc of
FIG. 8A;

[0028]FIG. 8C is a cross-sectional diagram taken along the arrow Xd-Xd of
FIG. 8A;

[0029]FIG. 9A is a perspective view showing the first type of stopper
shock-absorbing material of the second embodiment which corresponds to
the collar member of the third embodiment;

[0030]FIG. 9B is a cross-sectional diagram taken along the arrow Xe-Xe of
FIG. 9A;

[0031]FIG. 10A is a perspective view showing the second type of stopper
shock-absorbing material of the second embodiment which corresponds to
the collar member of the third embodiment;

[0032]FIG. 10B is a cross-sectional diagram taken along the arrow Xf-Xf of
FIG. 10A;

[0035]FIG. 11C is a perspective view showing a state in which the stopper
shock-absorbing materials are attached to the attachment tools; and

[0036]FIGS. 12A and 12B are graphs each showing the characteristics of the
present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037]Embodiments of the present invention will now be described
hereinafter with reference to the drawings. First, as shown in FIG. 1,
the present invention is mainly configured by a movable bracket 1, a
fixed bracket 2, a collar member 6, and stopper shock-absorbing materials
8. Supporting side portions 11, 11 are formed on both sides in a width
direction of the movable bracket 1. A bottom surface portion 12 which
integrally couples the both supporting side portions 11, 11 together is
formed underneath.

[0038]Also, a steering column 3 is disposed at upper end positions of the
both supporting side portions 11, 11, and this steering column 3 is
welded and fixed in a state such as to be roughly held between the both
supporting side portions 11, 11 (see FIG. 1B). Adjusting long holes 13,
13 for performing telescopic adjustment are formed on the both supporting
side portions 11, 11 of the movable bracket 1. Each adjusting long hole
13 is formed along a longer direction of the steering column 3 attached
to the movable bracket 1.

[0039]Next, the fixed bracket 2 is a component which attaches the movable
bracket 1 to a predetermined position within a vehicle and for performing
tilt/telescopic adjustment. As shown in FIG. 1B, the fixed bracket 2 is
configured by a pair of right and left fixed supporting side plates 21,
21 and an attachment apex 22. The fixed bracket 2 is attached to a
predetermined position within the vehicle via a capsule member and is
configured to be capable of absorbing shock energy generated at the time
of collision and the like.

[0040]Moreover, tilt adjusting holes 23, 23 are formed on the both fixed
supporting side plates 21, 21 of the fixed bracket 2. The positions of
the tilt adjusting holes 23, 23 are aligned with the positions of the
adjusting long holes 13, 13 of the movable bracket 1, and a lock shaft 5
is inserted into these holes (see FIG. 1B). Then, the both supporting
side portions 11, 11 are attached in a state such as to be held between
the both fixed supporting side plates 21, 21 of the fixed bracket 2 so
that the both supporting side portions 11, 11 can be tightened and fixed
by the lock shaft 5 (see FIG. 1B).

[0041]The lock shaft 5 locks (tightens) and unlocks steering during
tilt/telescopic adjustment, and further serves to support the collar
member 6 between the both supporting side portions 11, 11. The collar
member 6 can freely move along with the lock shaft 5 through the
adjusting long hole 13 in the longer direction. An operation lever 4 for
performing tilt/telescopic adjustment is attached to the lock shaft 5 for
tightening and releasing purposes. The lock shaft 5 is in the form of a
bolt on which an outer screw portion 51 is formed, and is provided for
tightening and releasing by means of a nut member 52, a cam member 53 and
the like (see FIG. 1B).

[0042]Next, attachment tools 7 are members which serve to dispose and
attach stopper shock-absorbing materials 8 in the movable bracket 1. As
shown in FIG. 1A and FIG. 2A, the attachment tools 7 are disposed so as
to be placed within the movable bracket 1 and at both side sections in
the longitudinal direction of the adjusting long hole 13, respectively.
Practically the attachment tools 7 are fixed to the steering column 3 by
welding means, the steering column 3 being fixed to the movable bracket 1
(see FIG. 11A). Here, the longitudinal direction means a direction which
matches the longer direction or axial direction of the steering column 3,
and corresponds to a horizontal direction which follows the longer
direction of the steering column 3 in FIG. 1A. As described above, the
attachment tools 7 are placed along the longitudinal direction within the
movable bracket 1 and, more specifically, attached so as to be placed in
both end sections in the longer direction of the adjusting long hole 13
formed in the movable bracket 1 (see FIG. 2A).

[0043]The stopper shock-absorbing materials 8, 8 are attached to the both
attachment tools 7, 7 respectively, which are attached in the
longitudinal direction. Accordingly, when the movable bracket 1 and the
adjusting long holes 13 are moved in the longitudinal direction with
reference to the shaft portion of the lock shaft 5 coupling the movable
bracket 1 and the fixed bracket 2 together, the collar member 6 which is
rotatably supported by the lock shaft 5 abuts against each of the stopper
shock-absorbing materials 8 without abutting directly against the both
ends in the longer direction of the adjusting long holes 13.

[0044]There are a plurality of embodiments regarding the collar member 6.
In the first embodiment, the collar member 6 is formed into a
substantially hollow cylindrical shape as shown in FIG. 1C, FIG. 2 and
the like. A cylindrical shape portion 61 is formed in the central section
in the axial direction, and conical portions 62, 62 are formed on both
sides in the width direction of the cylindrical shape portion 61. The
cylindrical shape portion 61 configures a cylindrical shape section whose
diameter is constant throughout the region forming the cylindrical shape
portion 61 along the axial direction. Each conical portion 62 is formed
into a conical shape such that the diameter thereof gradually increases
toward the end portions in the axial direction of the collar member 6. A
rotatably supporting through-hole 63 is formed in the central position in
the diameter direction of the collar member 6. The collar member 6 has
the shape of a substantially bobbin and is symmetric with respect to the
center in the axial direction.

[0045]The configuration of the collar member 6 according to the second
embodiment is substantially the same as that of the collar member 6
according to the first embodiment, as shown in FIG. 5, but the central
section in the axial direction is formed as a smallest diameter portion
64, which is formed such that the diameter thereof gradually increases
toward the both sides in the axial direction. Furthermore, the outer
circumference of the collar member 6 along the axial direction is formed
into a substantially arched shape which curves at the central section in
the axial direction. Moreover, the collar member 6 according to the third
embodiment is formed into a complete cylindrical shape, as shown in FIG.
6 and FIG. 7. Specifically, the collar member 6 is formed such that the
diameter thereof is constant throughout the whole position along the
axial direction.

[0046]Each stopper shock-absorbing material 8 is configured mainly by an
elastic main body portion 81 and a projecting portion 82. The stopper
shock-absorbing material 8 is formed by an elastic material, such as a
rubber or synthetic resin, and is integrally formed by the elastic main
body portion 81 and the projecting portion 82. The elastic main body
portion 81 is formed into a substantially thick plate shape and
configures an abutted surface 811, which is the surface abutting against
the collar member 6. The abutted surface 811 is formed into substantially
rectangular or square shape. Both end sides in a width direction of the
abutted surface 811 are first brought into abutment against the collar
member 6, and after a certain time interval the central section in the
width direction of the abutted surface 811 abuts against or comes close
to the collar member 6.

[0047]End portions 811a, 811a on both sides in the width direction of the
abutted surface 811 are the sections which are brought into abutment
first when the collar member 6 and the stopper shock-absorbing material 8
about against each other. A central portion 811b in the width direction
of the abutted surface 811 abuts against or comes close to the collar
member 6 after the both of the end portions 811a, 811a abut against the
collar member 6 (see FIGS. 4A through 4C, FIG. 5 through FIG. 7, and the
like). The central portion 811b of the stopper shock-absorbing material 8
indicates the central point and the area adjacent thereto in the axial
direction.

[0048]As shown in FIG. 2A, FIGS. 8A and 8C, FIG. 9, FIG. 10 and the like,
the abutted surface 811 is formed as a concave surface having a
substantially arched cross-sectional shape along the vertical direction
thereof. The radius of curvature of the concave arched surface between
the both ends in the width direction of the abutted surface 811 and in
the vertical direction of the same is substantially equal to the diameter
of the cylindrical shape portion 61 of the collar member 6: that is, the
concave arched surface is formed such that its radius of curvature is
substantially equal to the diameter of the section where the collar
member 6 and the abutted surface 811 abut against each other (see FIG.
8C).

[0049]The arched surface is formed such that the axial direction thereof
follows the width direction of the elastic main body portion 81. As shown
in FIG. 8B, FIG. 9B and the like, the projecting portion 82 of the
stopper shock-absorbing material 8 is formed into a substantially flat
cylindrical shape and formed so as to project in a substantially
perpendicular direction from the rear surface of the elastic main body
portion 81. A guide groove 71 and a fitting hole 72 into which the
projecting portion 82 of the stopper shock-absorbing material 8 is
inserted and fitted are formed in each attachment tool 7 (see FIG. 11B),
whereby the projecting portion 82 of the stopper shock-absorbing material
8 is guided by the guide groove 71 and fitted and fixed into the fitting
hole 72 (see FIGS. 11A through 11C).

[0050]As to the shape of the abutted surface 811 of the stopper
shock-absorbing material 8, there are various embodiments in accordance
with the shape of the collar member 6 of the first through third
embodiments. First of all, in the stopper shock-absorbing materials 8 of
the first embodiment, which are applied to the collar member 6 of the
first embodiment described above, the abutted surface 811 is formed to
have the same arched cross-sectional shape along the width direction (see
FIG. 4, FIG. 8). The size in the width direction of the abutted surface
811 is represented as Wa. In addition, the size in the axial direction of
the cylindrical shape portion 61 of the collar member 6 is represented as
La, and the size between the outermost ends of the respective conical
portions 62, 62 as Lb. The size Wa is set to be larger than the size La
and smaller than the size Lb. Specifically, La<Wa<Lb is established
(see FIG. 2B).

[0051]When telescopic adjustment is performed in such a combination of the
collar member 6 and the stopper shock-absorbing materials 8, the collar
member 6 is first moved toward either one of the stopper shock-absorbing
materials 8 in the longitudinal direction, and, at the instant of
abutment of the collar member 6, the both end portions 811a, 811a in the
width direction of the abutted surface 811 first abut against the
inclined surfaces of the conical portions 62, 62, respectively. Then,
when the collar member 6 is further moved close to the stopper
shock-absorbing material 8, the stopper shock-absorbing material 8
gradually abuts (or sometimes only comes close) such that the central
portion 811b in the width direction of the abutted surface 811 comes
close to the cylindrical shape portion 61 as the both end portions 811a,
811a in the width direction of the abutted surface 811 are elastically
deformed.

[0052]In this manner, in the abutted surface 811 of the stopper
shock-absorbing material 8, the central section in the width direction of
the abutted surface 811 abuts against or comes close to the cylindrical
shape portion 61, while the both ends in the width direction of the
abutted surface 811 of the stopper shock-absorbing material 8 start to
abut against the both conical portions 62, 62 of the collar member 6,
respectively. Accordingly, the both end sections in the width direction
of the abutted surface 811 which is elastically deformed easily abut
against the conical portions 62, 62 of the collar member 6, respectively,
whereby the stopper shock-absorbing material 8 is subjected to not only
compressional deformation but also shear deformation at an early stage of
abutment between the stopper shock-absorbing material 8 and the collar
member 6. Therefore, as compared with the ordinary case where the entire
abutted surface 811 abuts against the collar member 6 at once, the amount
of deformation of the abutted surface 811 can be increased and more shock
load can be absorbed.

[0053]Specifically, a so-called second-stage abutment operation is
performed in which, at the instant of abutment between the collar member
6 and the stopper shock-absorbing material 8, the both end portions 811a,
811a of the abutted surface 811 abut against the collar member 6 first,
and after a certain time interval the central portion 811b of the abutted
surface 811 abuts against the outer circumferential surface of the collar
member 6 (see FIG. 4). Accordingly, quietness in abutment can be secured.
Therefore, the shock force generated when the collar member 6 and the
stopper shock-absorbing material 8 hit against each other during
telescopic adjustment can be further reduced, and quietness and
operational touch in telescopic adjustment can be improved.

[0054]Next, the stopper shock-absorbing materials 8 of the first
embodiment are applied to a collar member 6 of the second embodiment, and
in this case the abutted surface 811 is formed to have the same arched
cross-sectional shape along the width direction (see FIG. 5A). As
compared with the collar member 6 of the first embodiment, in the collar
member 6 of the second embodiment the cylindrical shape portion 61 and
the both conical portions 62, 62 are not formed explicitly, but the
central portion in the axial direction of the collar member 6 is formed
as the curving smallest diameter portion 64.

[0055]Therefore, in the abutted surface 811 of the stopper shock-absorbing
material 8 which abuts against the collar member 6, the both end sections
in the width direction first abut the outer circumferential surface of
the collar member 6, and then the central section in the width direction
of the abutted surface 811 gradually abuts against the outer
circumferential surface of the collar member 6 (see FIGS. 5B and 5C). In
the case of the collar member 6 of the second embodiment, because the
outer circumferential surface thereof is formed into an arched shape
along the axial direction, the step of abutting the both end portions
811a, 811a in the with direction first and then the central portion 811b
of the abutted surface 811 of the stopper shock-absorbing material 8 has
continuity and allows extremely quiet telescopic adjustment operation.

[0056]Next, stopper shock-absorbing materials 8 of the second embodiment
which are applied to a collar member 6 of the third embodiment are each
formed such that the both end sections in the width direction of the
abutted surface 811 project. There are two types in the stopper
shock-absorbing materials 8 of the second embodiment: in the first type
the abutted surface 811 is formed into a concave arch shape along the
width direction, as shown in FIG. 6A and FIG. 9; and in the second type,
edge projecting portions 811c, 811c, which project from an outer
circumference of this stopper shock-absorbing material 8 to a
substantially a flange shape, are formed at the both end portions 811a,
811a in the width direction of the abutted surface 811, respectively, as
shown in FIG. 7A and FIG. 10. Each edge projecting portion 811c is formed
to have a substantially triangular cross-sectional shape. The central
portion 811b between the edge projecting portions 811c, 811c forms a flat
surface, i.e., a cylindrical shape. Either type is formed such that the
both end portions 811a, 811a of the abutted surface 811 project more than
the central portion 811b in the width direction.

[0057]When telescopic adjustment is performed in such a combination of the
collar member 6 and the stopper shock-absorbing materials 8, the collar
member 6 is first moved toward either one of the stopper shock-absorbing
materials 8 in the longitudinal direction, and, at the instant of
abutment between the stopper shock-absorbing material 8 and the collar
member 6, the both end portions 811a, 811a in the width direction of the
abutted surface 811 of the first type first abut against the outer
circumferential surface of the cylindrical collar member 6. Then, the
both end portions 811a, 811a are compressed while being elastically
deformed, and then the central portion 811b abuts against (or sometimes
only comes close to) the outer circumferential surface of the collar
member 6 (see FIGS. 6B and 6C).

[0058]Next, in the case of the second type, the both edge projecting
portions 811c, 811c in the width direction of the abutted surface 811
first abut against the outer circumferential surface of the cylindrical
collar member 6. Then, the both edge projecting portions 811c, 811c are
compressed while being elastically deformed, and then the central portion
811b abuts against (or sometimes only comes close to) the outer
circumferential surface of the collar member 6 (see FIGS. 7B and 7C).
Then, the shock force generated when the collar member 6 and the stopper
shock-absorbing material 8 hit against each other during telescopic
adjustment can be further reduced, and quietness and operational touch in
telescopic adjustment can be improved. As described above, the stopper
shock-absorbing materials 8 of the first and second embodiments were
illustrated as the stopper shock-absorbing materials 8 applied to the
collar members 6 of the first through third embodiments, but the
combination of these components is not limited to the combinations
described above. Therefore, the combination of the collar members 6 of
the first through third embodiments and the stopper shock-absorbing
materials 8 of the first and second embodiments may be set arbitrarily,
and, for example, the stopper shock-absorbing materials 8 of the second
embodiment can be applied to the collar member 6 of the first embodiment.

[0059]FIG. 12 is a graph showing the characteristics of the present
invention. The graph of FIG. 12A shows that the performances drawn in
thick lines can be achieved at the point of a post-countermeasure at
which the present invention is applied. This post-countermeasure shows
that the stroke between when the collar member 6 and the stopper
shock-absorbing material 8 abut against each other and when they stop is
extended. Therefore, this graph shows that generation G, i.e., a shock,
between a pre-countermeasure and the post-countermeasure, is reduced.
FIG. 12B shows the magnitude of a shock which is caused by the difference
in telescopic speeds of abutment between the collar member 6 and the
stopper shock-absorbing material 8 during telescopic adjustment.
According to the present invention, the shock generated by the abutment
is reduced at all telescopic speeds.